As a compact exhaust gas purifying apparatus for purifying PM and NOx in an exhaust gas, there has been known one that has a casing, which houses a diesel oxidation catalyst (DOC) converter and a diesel particulate filter (DPF) and a casing, which houses a selective catalytic reduction (SCR) converter, the two casings being arranged in parallel in the direction of the vehicle width on the outer side of a frame, as disclosed in Japanese Laid-Open Patent Publication No. 2009-108685 (Patent Document 1).